TW200400240A - CMP slurry for metal and method for manufacturing metal line contact plug of semiconductor device using the same - Google Patents

Description

200400240

说明 Description of the invention (the description of the invention shall state: the technical field to which the invention belongs, the prior art, the content, the embodiments, and the drawings are briefly explained) The technical field to which the invention belongs It is a 'CMP' slurry. More specifically, the present invention discloses a method for manufacturing a metal wire contact plug of a semiconductor device, which uses an acidic CMP slurry for an oxide film including an oxidizing agent and a complexing agent, at a similar speed. The metal, oxide film and nitride film are polished, so it is easy to separate the metal wire contact plug. BACKGROUND OF THE INVENTION Generally, for a semiconductor of a Nando integrated circuit, the integrated device may include about 8,000,000 transistors / cm2. Therefore, for high integration, multiple layers of high-quality metal wires are needed to connect this device. Such a multi-layer metal wire can be realized by effective planarizing of a dielectric interposed between adjacent metal wires. Because of the need for a precise method for planarizing the wafer, a CMP process was developed. During the CMP process, chemicals that have good reactivity in the CMP slurry are used to chemically remove the materials to be removed. At the same time, the wafer surface was mechanically polished with an ultra-fine abrasive. CMP fabrication is performed by injecting a liquid slurry between the entire surface of the wafer and the rotating elastic pad. The conventional slurry used in the metal CMP process includes: abrasives such as S2O2, Al2O3, or Mn02; oxidants, such as H202, H5I06, or FeN03, are used to oxidize the metal to form an oxide film, thereby promoting the surname Carving process; a small amount of sulfuric acid, nitric acid or hydrochloric acid is used to make the slurry acidic; dispersant; compounding agent; and buffering agent. When the conventional slurry is used to remove metal by the CMP process, the metal surface is oxidized by an oxidizing agent, and then the oxidized part is processed by the abrasive contained in the slurry. 200400240 Invention Description Continued (2) Mechanical polishing and removal. However, since the above-mentioned CMP slurry for metal is relatively expensive, increasing the unit cost of the CMP process also increases the cost of manufacturing the entire device. Therefore, a new slurry has been developed that can easily polish the metal with only a small amount of slurry, thereby controlling costs. Hereinafter, a conventional method of manufacturing a metal line contact plug of a semiconductor device will be described with reference to the drawings.

FIG. La is a top view after the bit line pattern is formed. Figure lb is a top view after the worm-etched metal wire contacts the plug. 2a to 2d illustrate a conventional method of manufacturing a metal wire contact plug of a semiconductor device. Referring to FIG. 2a, a diagram illustrating a state in which the interlayer insulating g film is stacked on the A-A1 yellow section in FIG.

A bit line layer (not shown) and a mask insulating film (not shown) are formed on the semiconductor substrate 11. Then, the bit line pattern 13 on which the mask insulating film pattern 15 is stacked is formed on the semiconductor substrate 11 by etching the obtained surface. Herein, a mask insulating film (not shown) is formed using a nitride film having a thickness of t !. Thereafter, an interlayer insulating film 17 is formed on the top surface of the resulting structure using an oxide film. Referring to FIG. 2b, a diagram illustrating a cross section B of FIG. 1b is shown. The interlayer insulating film pattern 17-1 and the metal line contact hole 19 are formed by etching the interlayer insulating film 17 using a metal line contact mask (not shown) as an etching mask. Herein, a region “C” shown in FIG. 1b represents a region in which a metal 200400240 is formed by etching the interlayer insulating film 17 (3) I. Description of the Invention Continuation line line contact hole 19 represents a region, and a region “D” represents A region in which the metal line contact hole 19 is not formed.

An oxide film (not shown) having a predetermined thickness is deposited on the obtained structure, and then the oxide film is etched to form an oxide spacer 21 on the sidewall of the metal line contact hole 19, the mask insulating film pattern 15 and the bit line 13. . Here, the thickness of the mask insulating film pattern 15 formed in the metal line contact hole 19 is reduced to t2 due to an etching process for forming the metal line contact hole 19 and forming the oxide film spacer 21. Referring to Fig. 2c, a metal layer 23 is stacked on the resulting structure. Herein, the metal layer 23 has a step coverage of t3 in the metal line contact hole 19 and a step coverage of t4 from the mask insulating film pattern 15-1. Referring to FIG. 2d, the metal line contact plug 25 is formed by removing a part of the metal layer 23, the interlayer insulating film 17-1, and the oxide film spacer 21 using a CMP process. In this paper, in order to separate the metal wire contact plug 25 into P1 and P2 by the CMP process, it is necessary to use slurry to polish the depth of t4 to remove part of the metal layer 23.

The polishing speed should be similar between the films in order to remove the multilayer film above. However, when the metal is polished using a conventional CMP slurry for metal, the polishing speed of the metal layer is more than 20 times faster than that of the oxide film. The polishing speed of the film or nitride film is not easy to remove, so the metal wire contact plug is not separated, and the polishing processing time is increased. In other words, as shown in Fig. 3-30, the uniformity in the wafer is reduced and the phenomenon of equipment vibration is generated, resulting in a decrease in the stability of the method. 200400240 (4) I Description of Invention Continued In addition, since the above CMP process has a fast polishing speed in peripheral circuit regions with a low pattern density, a mask insulating film pattern (on a bit line on a peripheral circuit region (not shown)) is formed ( (Not shown) is damaged before the metal line contact plug is completely separated, exposing the bit line (not shown). As a result, a bridge is formed between the devices, and leakage current is increased, resulting in a decrease in device reliability and operating characteristics. To overcome the above problems, a CMP slurry for polishing multiple layers can be used. For example, USP 6,200,875 discloses a method for forming a capacitor in which a contact plug is formed by simultaneously polishing a crushed film and an oxide film using a CMP slurry for an oxide film. However, the composition of the CMP paddle fluid for an oxide film is not described in the patent. SUMMARY OF THE INVENTION Accordingly, the present invention discloses a CMP slurry for metal, which can easily separate a metal wire contact plug by polishing a nitride film, an oxide film, and a metal layer at a similar speed. The invention also discloses a method for preparing a metal wire contact plug of a semiconductor device by using the CMP slurry. Embodiments The present invention discloses a CMP slurry for a metal. The acidic CMP slurry for an oxide film further includes an oxidizing agent and a complexing agent and can easily separate a metal by polishing a nitride film, an oxide film, and a metal layer at a similar speed. Line contact plug. The CMP slurry preferably used for the oxide film has a pH of 2 to 7 and contains an oxidizing agent and a complexing agent. As a result, the disclosed CMP slurry for metal had a pH of 2 200400240 (5). The polishing selectivity of the CMP slurry of the present invention for a nitride film: an oxide film: a metal layer is in a range of 1: 1 to 2] to 3. The polishing selectivity is similar. The oxidizing agent that oxidizes the metal to increase the polishing rate is selected from the group consisting of H202, H5I06, FeN03, and combinations thereof. Herein, the oxidant is present in an amount of 0.5 to 10% by volume, preferably 2 to 6% by volume, based on the CMP slurry.

The compounding agent forms a compound with the metal dropped during the polishing process to prevent the accumulation of polishing by-products. The complexing agent is selected from the group consisting of a carboxyl (-COOH) -containing hydrocarbon compound such as tartaric acid, a nitro (-NO2) -containing hydrocarbon compound such as nitroglycerin, an ester group (-COO-)-containing hydrocarbon compound, and an ether group (- 〇-) 'hydrocarbon compounds, amine group (-NH2) -containing hydrocarbon compounds such as ethylenediamine and a combination of groups. Herein, the complexing agent has a molecular weight of 40 to 1000, and preferably the complexing agent is selected from the following formulae 1 to 13: Formula 1 OH 0

〇II C——OH

-10- 200400240 Description of the Invention Continued ⑹ Formula 3 〇 II R— II -c——OH Formula 4 NO

no2 Formula 6 〇

R II

R——c—〇——R Formula 7 〇 〇

R II II

R-C—O-C—R Formula 8

R-〇-R Formula 9

HO-H2C——〇——R formula 10 R——NH2 formula 11 〇

p II R—c—〇—nh2 200400240 _ (7) Description of the invention continued on formula 12 〇

II R——C——CH2——NH2 Formula 13 〇

II R——C——NH2 where R is a branched or linear substituted C | -C5 () alkyl or aryl.

The compounding agent is present in an amount of 0.001 to 5% by volume based on the CMP slurry. When the amount exceeds 0.001 to 5% by volume, the chemical etching ability is increased due to the increase of chemical elements, which causes the CMP process to deteriorate. Therefore, the amount of the compounding agent added is less than 5% by volume, preferably in the range of 0.01 to 1% by volume. The general compounding agent contained in the slurry used in the general metal CMP process forms a compound with the metal dropped during the polishing process to prevent the polishing by-products from accumulating again.

The disclosed composite agent promotes the oxide film formed on the metal surface to be easily polished by the oxidizing agent, and destroys the metal-oxide film bond to remove the metal. When the acidic slurry in the CMP process used to form the metal wire contact plug does not contain an oxidizing agent or a complexing agent or contains only one of them, the polishing speed of the metal does not change. However, when the acid slurry contains both an oxidizing agent and a compounding agent mixed in an appropriate ratio, the metal polishing speed can be significantly increased. The CMP slurry includes an abrasive, and the abrasive is selected from the group consisting of Si02, Ce02, Zr02, A1203, and combinations thereof. Herein, the slurry contains an abrasive in an amount of 0.5 to 30% by weight, preferably 10 to 30% by weight, based on the CMP slurry. The CMP slurry contains an abrasive in an amount of 0.5 to 30% by weight based on the CMP slurry. Research-12-200400240 (8) Description of the invention Continuation sheet abrasive: oxidant H2O2 with a volume ratio of 3 to 4.1, and oxidant: The volume ratio of the compounding agent is 20 to 50: 1, and then a CMP slurry for metal having a polishing selectivity in a range of nitride film: oxide film: metal structure 1] to 2: 1 to 3 is obtained. . The CMP slurry for metal of the present invention further includes a dispersant and a buffer. The invention also provides a method for manufacturing a metal wire contact plug of a semiconductor device, which method comprises:

Forming a stacked pattern of bit lines and a mask insulating film pattern on a semiconductor substrate; forming an intermediate layer insulating film on the entire surface of the resulting structure; selectively etching away the intermediate layer insulating film to form a metal wire connection hole; Forming an oxide film spacer on a sidewall of a metal line contact hole, on a stacked pattern of bit lines, and on a mask insulating film in the metal line contact hole; depositing a metal layer on the entire surface of the resulting structure; and using the slurry of the present invention A CMP process is performed to form a metal line contact plug.

The mask insulating film is a nitride film and the interlayer insulating film is an oxide film. The metal layer is selected from the group consisting of TiN, W, and Al layers, alloys thereof, and combinations thereof. Hereinafter, the CMP slurry of the present invention and the manufacturing method of the present invention will be described in detail with reference to the drawings. FIG. 4a is a top view after the bit line pattern is formed. Figure 4b is a top view of the metal wire contact plug after etching. 5a to 5d illustrate a method for preparing a metal wire contact plug of a semiconductor device using the acidic CMP slurry of the present invention. -13-200400240 (9) Continued description of the invention Referring to Fig. 5a, a diagram illustrating a state where the interlayer insulating film is stacked on the cross section E-E 'of Fig. 4a. A bit line layer (not shown) and a mask insulating film (not shown) are formed on the semiconductor substrate 101. A diffusion barrier film (not shown) and a metal layer (not shown) are sequentially formed on the bit line layer. Out). Subsequently, the obtained structure is etched to form a bit line pattern 103 on which a mask insulating pattern 105 is stacked.

Here, a diffusion barrier film (not shown) is formed from Ti / ΉN by a chemical vapor deposition (CVD) method using TiCl4 as a source. The metal layer (not shown) is formed of tungsten. The mask insulating film (not shown) is formed of a nitride film by a plasma chemical deposition method at a temperature of 5 ° to 600 ° C, and has a thickness of q. Next, on the top surface of the resulting structure, an interlayer insulating film 107 is formed using an oxide film.

Referring to Fig. 5b, a cross section F-Ff of Fig. 4b is illustrated. The interlayer insulating film pattern 107-1 and the metal line contact hole 109 are formed by etching the interlayer insulating film 107 using a metal line contact mask (not shown) as an etching mask. Herein, the area “G” shown in FIG. 4b represents the area where the metal line contact hole 109 is formed by etching the interlayer insulating film 107 and the area “Η” represents the area where the metal line contact hole 109 is not formed. An oxide film (not shown) of a predetermined thickness is formed on the obtained structure, and then the top surface of the metal line contact hole 109, the bit line pattern 103, and the mask insulating film pattern 105 are etched by etching the top surface of the structure to deposit it. The oxide film spacer 111 is formed. 200400240 (10) Description of the invention continued in this text, the thickness of the mask insulating film pattern 105 in the metal line contact hole 109 is due to the etching of the metal line contact hole 109 and the oxide film spacer 111 The process is reduced to t2. Referring to FIG. 5c, a metal layer 113 is deposited on the obtained surface. In this paper, an atomic layer deposition (ALD) process is used to deposit a metal layer 113 composed of TiN, which has a t3 The step-type cover layer has a step-type cover layer t4 from the mask insulating pattern 105.

Because TiN has excellent activity, it can be easily polished by the slurry of the present invention. The slurry of the present invention can be used during a wire polishing process using W or A1 other than TiN. Referring to Fig. 5d, a CMP slurry for metal using the traces of the present invention is used to perform a CMP process on a metal layer 113, an interlayer insulating film 107-1, an oxide film spacer, and a mask insulating film pattern 105 of a predetermined thickness. As a result, a uniform metal wire contact plug 115 is formed in which the region P1 and the region P2 are completely separated.

Since the metal layer 113, the interlayer insulating film pattern 107-1, the oxide film spacer 111, and the mask insulating film pattern 105 are sequentially polished using a CMP process at a thickness greater than t4, the mask on the bit line 103 is insulated The thickness of the thin film pattern 105 is reduced to t5 (which is less than t2). When the intermediate layer insulation pattern 107-1 is exposed, the entire surface of the metal layer 113 may be etched by dry etching. Therefore, 80 to 90% of the deposited thickness of the metal layer is subsequently removed. The CMP slurry of the present invention can be used to perform a CMP process on an oxide film, and it also has an excellent polishing effect for polishing a metal layer with good reactivity. In other words, if the CMP process of the present invention is used for the CMP process, the -15-200400240 can be prevented (11) Description of the continued sheet The metal wire contact plug is not sufficiently separated because the metal layer with the low-step cover layer is not sufficiently removed. Therefore, the dependence on the CMP equipment is reduced, it is easy to carry out subsequent processes by planarization, and the insulation characteristics between the metal wire contact plugs are improved.

The acidic CMP slurry for an oxide film of the present invention, which also includes an oxidizing agent and a complexing agent to adjust the polishing speed of a nitride mask, an oxide film, and a metal layer on a wafer, will be described in more detail with reference to the following examples. Note that these examples should not be used to limit the present invention. The comparative example uses a CMP slurry for an oxide film having a pH of 3 and a 30% by weight SiO2 abrasive. The CMP equipment was used to mask the crystals at a pressure of 3 psi and a belt speed of 700 fpm. The high-density plasma (HDP) oxide film, SiN film, and TiN film are polished on the circle. Then, the polishing speed of each film was measured and shown in Table 1. Example 1

The oxidant H2O2 was added to a CMP slurry for an oxide film having a pH of 3 and containing 30% by weight of a SiO2 abrasive so that the weight ratio of the abrasive: oxidant was 4: 1. Then, a compound of formula 1 as a complexing agent was added to the CMP slurry so that the weight ratio of the oxidizing agent to the complexing agent was 40: 1, thereby obtaining a CMP slurry for metal. Using the CMP slurry for metal prepared above, a high-density plasma HDP oxide film, a SiN film, and a TiN were masked on a masking wafer by a CMP apparatus at a head of 3 psi and a belt speed of 700 fpm. The film is polished. Then, the polishing speed of each film was measured and shown in Table 1. • 16- 200400240 Description of the Invention Continued (12) Example 2 In a CMP slurry for an oxide film, an oxidant H2O2 plus SiJ pH 3 and containing 30% by weight of a SiO2 abrasive was used to make the abrasive: The weight ratio of the oxidant is 3: 1, and then deionized water with the same weight as the oxidant is added. Next, a compound of formula 1 as a complexing agent was added to the CMP slurry so that the weight ratio of the oxidant: composite was 40: 1, thereby obtaining a CMP slurry for metal.

Using the CMP slurry prepared above, the procedure of Example 1 was repeated. Then, the polishing speed of each film was measured and shown in Table 1. Example 3 In a CMP slurry for an oxide film, an oxidant H2O2 plus S! J at pH 3 and 30% by weight of a SiO2 abrasive was used so that the abrasive: oxidant weight ratio was 4: 1. Then, a compound of formula 1 as a complexing agent is added to the CMP slurry so that the weight ratio of the oxidizing agent to the complexing agent is 40: 1, thereby obtaining a CMP slurry for metal. Using the CMP slurry for metal prepared as described above, by using a CMP equipment,

The high-density plasma HDP oxide film, SiN film, and TiN film were polished on a masking wafer at a 5 psi indenter and a belt speed of 700 fpm. Then, the polishing speed of each film was measured and shown in Table 1. Example 4 An oxidant H202 was added to a CMP slurry for an oxide film having a pH of 3 and containing 30% by weight of a SiO2 abrasive, so that the abrasive: oxidant weight ratio was 4: 1. Then, a compound of formula 1 as a complexing agent was added to the CMP slurry so that the weight ratio of the oxidizing agent to the complexing agent was 40 · 1, thereby obtaining a CMP slurry for metal. -17-200400240 (13) Description of the invention Continuation sheet The above-mentioned CMP slurry for metal was used to align the high-density on a masking wafer with a CMP equipment at a 6 psi indenter and a 700 fpm belt speed. Plasma HDP oxide film, SiN film and TiN film are polished. Then, the polishing speed of each film was measured and shown in Table 1. Table 1] Polishing speed (unit: A / min) Nitride film (SiN) HDP oxide film metal (TiN) Comparative example 1917 2994 625 Example 1 1800 2432 4000 Example 2 1291 1816 3261 Example 3 2524 3525 3261 Implementation Example 4 2685 4052 3352

The graph of FIG. 7 illustrates the polishing selectivity of the oxide film / nitride film, the oxide film / metal, and the metal / nitride film, which are calculated using the polishing speed measured in the embodiment. The results show that when the slurry for an oxide film including the oxidizing agent and the complexing agent of the present invention is used, the oxide film, the nitride film, and the metal all have similar polishing selectivity, and the use of the non-oxidizing agent and the complexing agent is similar. This is not the case with the oxide film slurry. As mentioned above, by using an acidic CMP slurry for an oxide film that also includes an oxidizing agent and a complexing agent, the metal wire contact plug can be easily separated by a CMP process. The CMP slurry polishes the nitride film and oxidizes at a similar rate. Film and metal.

In addition, the CMP slurry conventionally used for Polygonum is 10 times more expensive than the CMP slurry conventionally used for oxide films. Therefore, if the oxide film CMP-18-200400240 of the present invention is used in the description of the invention Continued (14) The slurry is used to perform the CMP process on the metal, which can reduce the process cost and reduce the dependence on the CMP equipment. In addition, since the areas of the metal wire contact plugs are completely separated, the insulation characteristics between the metal wire contact plugs, which makes subsequent processing easier, are improved. Brief Description of the Drawings Figure la is a top view after the bit line pattern is formed. Figure lb is a top view after the metal line contact plug is etched.

2a to 2d schematically illustrate a conventional method of manufacturing a metal wire contact plug of a semiconductor device. Figure 3 is a CD SEM photograph of a conventional metal wire contact plug. FIG. 4a is a top view after a bit line pattern is formed according to the present invention. FIG. 4b is a top view after the metal line contact plug is etched according to the present invention. 5a to 5d schematically illustrate a method for manufacturing a metal wire contact plug of a semiconductor device according to the present invention. FIG. 6 is a CD SEM photograph of a metal wire contact plug of the present invention.

FIG. 7 is a graph illustrating the polishing speed and selectivity when polishing metal, oxide and nitride films in a blanket wafer using the disclosed CMP polymer liquid. Description of Symbols for Symbols 11, 101: Semiconductor substrates 13, 103: Bit line patterns 15, 105: Mask insulation patterns 17-1, 107-1: Interlayer insulation film patterns 19, 109: Metal line contact holes- 19- 200400240 (15) Description of the invention continued on 21, 111: oxide spacer 113: metal wire 23, 115: metal wire contact plug

-20-

Claims (1)

200400240 Scope of application and patent application 1. A chemical mechanical polishing (CMP) slurry for an oxide film, which has a pH of 2 to 7 and includes an oxidizing agent and a complexing agent. 2. The CMP slurry according to item 1 of the patent application scope, wherein the CMP slurry has a pH of 2 to 3. 3. For example, the CMP slurry of the scope of application for patent, wherein the CMP slurry has a polishing option of nitride film: oxide film: metal layer of 1: 1 ~ 2: 1 ~ 3 Sex. 4. For example, the CMP slurry of the scope of patent application, wherein the oxidant is selected from the group consisting of H202, H5I06, FeN03 and combinations thereof. 5. The CMP slurry according to item 1 of the patent application scope, wherein the oxidant is present in an amount of 0.5 to 10% by volume based on the CMP slurry. 6. The CMP slurry according to item 1 of the patent application scope, wherein the oxidant is present in an amount of 2 to 6% by volume based on the CMP slurry. 7. The CMP slurry according to item 1 of the patent application scope, wherein the complexing agent is selected from the group consisting of a carboxyl (-COOH) -containing hydrocarbon compound, a nitro (-N02) -containing hydrocarbon compound, and an ester group (-COO-) A group of hydrocarbon compounds, hydrocarbon compounds containing acid groups (-0-), hydrocarbon compounds containing amine groups (-NH2), and combinations thereof. 8. For the CMP slurry of item 7 in the scope of patent application, wherein the compounding agent is selected from the group consisting of the following formulas 1 to 13: Formula 1 〇 OH 0 HO 200400240 Patent Application Fan Continued Form 2 〇 II C——OH Formula 3 〇 II R——C—OH Formula 6 〇R II RC-〇-R Formula 7 〇 〇R II II R——C——〇——C—R Formula 8 R—〇—R Formula 9 HO——H2C——〇—R 200400240 Apply for a patent Range Continued Formula 10 R——NH2 Formula 11 〇II R——C—〇—nh2 Formula 12 〇II R——C——CH2——NH2 Formula 13 〇II R——C——NH2 where R is a branch Chain or straight 4 substituted Q-C50 alkyl or aryl. 9. The CMP slurry as claimed in claim 7 wherein the compound has a molecular weight of 40 to 1,000. 10. The CMP slurry according to item 1 of the patent application scope, wherein the compounding agent is present in an amount of 0.001 to 5% by volume based on the CMP slurry. 11. If the CMP slurry of item 10 of the patent application range, the compounding agent is present in an amount of 0.01 to 1% by volume based on the CMP slurry. 12. The CMP slurry according to item 1 of the patent application scope, wherein the slurry includes abrasives selected from the group consisting of Si02, Ce02, Zr02, Al203 and combinations thereof. 13. The CMP slurry according to item 1 of the patent application scope, wherein the CMP slurry includes an abrasive in an amount of 0.5 to 30% by weight. 14. The CMP slurry according to item 1 of the patent application scope, wherein the CMP slurry includes an abrasive in an amount of 10 to 30% by weight. 15. For example, the CMP slurry of item 1 of the patent application scope, wherein the CMP slurry includes an abrasive in an amount of 0.5 to 30% by weight of the CMP slurry; abrasive 200400240 patent application scope continued: the volume ratio of the oxidant is 3 ~ 4 : 1 oxidant; and the volume ratio of oxidant: composite agent is 20 ~ 50: 1 compounder of formula 1 below: [Formula 1] OH 0 16. The CMP slurry according to item 15 of the patent application, wherein the abrasive is SiO 2 and the oxidant is H202. 17. A method of manufacturing a metal wire contact plug for a semiconductor device, which includes a CMP process using a CMP slurry such as the one in the scope of patent application. 18. A method of manufacturing a metal wire contact plug for a semiconductor device, the method comprising: forming a stacked pattern of bit lines and a mask insulating film pattern on a semiconductor substrate; forming an interlayer insulating film on the entire surface of the resulting structure; Selectively etching away the interlayer insulating film to form a metal line contact hole; forming an oxide film spacer on the sidewall of the metal line contact hole, on the bit line stack pattern, and on the mask insulating film in the metal line contact hole; Depositing a metal layer on the entire surface of the resulting structure; and performing a CMP process using a CMP slurry such as the one in the scope of patent application to form a metal wire contact plug. 19. The method according to claim 18, wherein the mask insulating film is a nitride film. 200400240 Patent Application Continued 20. The method according to item 18 of the Patent Application, wherein the interlayer insulating film is an oxide film. 21. The method of claim 18, wherein the metal layer is selected from the group consisting of TiN, W, A1, an alloy thereof, and a combination thereof.